For many years, philosophers asked, "if a tree falls in the forest and no one is there to hear it, does it make a sound?" Scientists answered that question and went on to figure out how fast that sound traveled. Calculating that speed was not as simple as it seemed. Unlike the speed of light, the speed of sound is not constant, and different variables change how fast it travels. Scientists persevered and now understand how sound works, whether it's the voice of a soprano or a tree crashing to the ground.


1. What is Sound?

Sound is energy created by vibrations. When objects vibrate, they cause the particles around them to vibrate, which in turn cause more particles to vibrate. This is a sound wave. For example, if a tree falls to the ground, the vibrations caused by its landing create a sound wave. Sound waves continue until they run out of energy and if there are ears within the range of the wave, it can indeed be heard.

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